Chalcedony with Druzy Quartz Geode

Physical Properties

Hardness: 6.5-7 (Mohs); Color: Greyish-blue chalcedony with a sparkly, colorless druzy center; Luster: Waxy to vitreous; Crystal structure: Trigonal/Hexagonal; Cleavage: None; Fracture: Conchoidal.

Formation & Geological History

Formed by the deposition of silica-rich groundwater within cavities of volcanic or sedimentary rocks. Over time, layers of microcrystalline quartz (chalcedony) form the rim, while macroscopic crystals (druzy quartz) precipitate in the center.

Uses & Applications

Predominantly used for ornamental purposes, lapidary work (cabs), jewelry, and as a collector's mineral specimen.

Geological Facts

The 'bumpy' texture seen in the center is called a 'druzy' coating, which consists of thousands of tiny, sparkling quartz crystal points. This specific specimen has a somewhat botryoidal (grape-like) chalcedony base under the crystals.

Field Identification & Locations

Identify in the field by looking for vugs or cavities in host rocks (like basalt). It will have a characteristic waxy exterior and will be hard enough to scratch glass. Commonly found in riverbeds or volcanic regions.

Identified on: 4/19/2026

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